Laminated packaging material, a method of producing the same, as well as a packaging container produced from the packaging material

ABSTRACT

A laminated packaging material ( 10 ) comprising a core layer ( 11 ) and a barrier layer ( 14 ) formed from a liqueform composition comprising a dispersion or solution of a polymer, starch or starch derivative on one side of the core layer, the barrier layer also including particles of amorphous SiO 2 . According to the invention, said particles of amorphous SiO 2  in colloidal particle size in said barrier layer are present in a content of above 40 weight % but below 80 weight %. The invention also relates to a packaging container which has been produced from the packaging material, as well as a method of producing the packaging material.

TECHNICAL FIELD

The present invention relates to a laminated packaging materialcomprising a core layer and a barrier layer formed from a liqueformbarrier composition comprising a dispersion or solution of a polymer,starch or starch derivate, on one side of the core layer, the barrierlayer also including particles of amorphous SiO₂. The present inventionfurther relates to a packaging container which has been produced fromthe packaging material, as well as a method for producing the packagingmaterial.

BACKGROUND ART

Within the packaging industry, it is well known to employ laminatedpackaging materials of a single-use disposable nature for the packingand transport of liquid foods. Normally, such laminated packagingmaterial is built up from a configurationally rigid but foldable corelayer, for example consisting of paper or paperboard, in order to obtaingood mechanical configurational stability. Liquid-tight coatings ofplastic are laid on both sides of the core layer and protect theliquid-absorbing fibres of the core layer effectively from beingpenetrated by moisture. These outer layers normally consist of athermoplastic, preferably polyethylene, which moreover imparts to thepackaging material superior thermosealing properties so that thepackaging material may be converted into finished packages of thedesired geometric configuration.

However, laminated packaging material which consists solely of paper orpaperboard and liquid-tight plastic lacks tightness against gases, inparticular oxygen gas. This is a major disadvantage in the packing ofmany foods whose shelf-life declines dramatically when they come intocontact with oxygen gas, for example fruit juices. In order tosupplement the packaging material with a barrier against gases, inparticular against oxygen gas, it belongs to the prior art technology tolay on a layer possessing superior tightness to oxygen gas, for examplealuminium foil or polyvinyl alcohol, on that side of the core layerwhich is intended to face in towards the interior of the package.

In comparison with aluminium foil, polyvinyl alcohol possesses manydesirable properties, for which reason it is to be preferred as abarrier material in many contexts. Among other things, polyvinyl alcoholpossesses higher mechanical strength, better compatibility with foodsand is more economical, at the same time as enjoying excellentproperties as an oxygen gas barrier. It has further been deemed as asuitable material, in certain cases from the environmental viewpoint orwith a view to recycling and recovery to replace aluminium foil as gasbarrier material in food packages.

One drawback is that polyvinyl alcohol is sensitive to moisture andrapidly loses its barrier properties when it is exposed to a dampenvironment. This drawback was previously obviated according toWO97/22536 in that the polyvinyl alcohol was combined with one or moreper se known, food approved polymers, for example copolymersethylene/acrylic acid (EAA) or copolymers of styrene/butadiene. Theseform, in combination with polyvinyl alcohol, a continuous and unitarylayer with superior properties as gas barrier, in particular againstoxygen gas, at the same time as the desired superior gas barrierproperties of the polyvinyl alcohol are retained also in a dampenvironment.

While polymer gas barrier materials may impart good gas barrierproperties to a packaging laminate, they are nevertheless to some extentpermeable for oxygen gas, while a material of a type such as metal orglass for cans or bottles possesses an oxygen gas permeability which ispractically zero. In order further to improve the gas barrierproperties, it is possible to mix the polymer gas barrier material withan inorganic lamellar material. Such a polymer composition for gasbarrier material is described, for example, in EP-A-O 590 263 andpossesses excellent barrier properties against gas and moisture. Thus,EP-A-O 590 263 presents a method for the production of a polymercomposition for a gas barrier material, or the formed product, e.g. afilm, the composition including a polymer and an inorganic lamellarmaterial with a particle size of 5 μm or less and a quantityrelationship of 50-5000, and the method comprises the step that theinorganic laminate material is dispersed in a polymer or a polymersolution in such a state that the inorganic lamellar material swells orshears up in a solvent/dispersion agent, whereafter this is removed fromthe dispersion when necessary in the form of a film, at the same time asthe lamellar material remains in the swollen state.

From JP 56004563 is also known a plastic material which, with a view toattaining superior gas and moisture barrier properties, has been coatedwith a film of polyvinyl alcohol (PVOH) and SiO₂. The relationshipSiO₂/PVOH may be 5/95-80/20. It is also disclosed that the size of theSiO₂ particles does not constitute a limitation but that they shouldhave an average diameter of below 100 micron. It is further disclosedthat an aqueous dispersion which contains PVOH and SiO₂ is utilised forthe coating and that thermocuring may be carried out, for example duringa period of time of up to an hour in a temperature of 80-200° C.

According to JP10-001515, the intention is to crosslink the main chainsin PVOH by means of SiO₂. The purpose is, in a laminate with a corelayer of paperboard, to improve gas barrier properties despite a dampand humid environment.

WO 99/44826 describes a laminate with a core layer of biaxially orientedpolypropylene. An outer layer may consist of a homo- or copolymer of avinyl alcohol which may include an “antiblocking agent”. Such an“antiblocking agent” may consist of spherical SiO₂ particles of theorder of magnitude of 1-6 μm, in a quantity of 0.1-2 weight %.

EP 761 876 describes a packaging laminate for, for example, a packagefor liquid foods, the laminate being built up with a core of paperboard.A coating layer on the paperboard, the coating layer including PVOH andamorphous SiO₂ has for its purpose to act as a moisture and aromabarrier.

WO 00/40404 describes a thermoplastic film intended for the packing offood products, e.g. by wrapping them in a transparent film, but notintended for the production of dimensionally stable packages for liquidfoods. The film according to WO 00/40404 has a coating layer on at leastone surface thereof, the coating layer including a polymer binder oradhesive and an additive including nanoparticles of, for example, SiO₂.It is disclosed that the nanoparticles preferably constitute 5 to 20weight % of the additive, and that the additive constitutes 40 to 90weight % of the coating.

BRIEF SUMMARY OF THE INVENTION

The present invention has for its object, in comparison with prior arttechnology, to further optimise the gas barrier properties in a layerwhich is formed from a liqueform composition comprising a dispersion orsolution of a polymer, starch or starch derivate and particles ofamorphous SiO₂. In particular, the present invention has for its object,in such a layer, to attain increased oxygen gas barrier and increasedliquid resistance. The reason for this is that it has been found, inconnection with the evolution of the present invention, that asurprisingly good effect may be attained in certain selective criteriafor the composition of the layer. According to the present invention,such an optimated layer is intended to be employed in a laminatepackaging material possessing excellent barrier properties, inparticular against gases, the packaging material in turn being intendedto be employed in a package possessing excellent barrier properties.

It is also an object of the present invention to realise a laminatedpackaging material possessing improved rigidity.

The packaging material which is provided with a layer of the oxygen gasbarrier comprising polymer, starch or starch derivate and SiO₂ accordingto the present invention may include a core layer, i.e. that layer whichmakes the greatest contribution to the thickness of the material and toits mechanical properties, the core layer consisting of a layer of paperor paperboard or a layer of a polymer material.

The selective criteria requisite for the improved barrier effect andrigidity are accounted for in appended claim 1, relating to a laminatepackaging material. The claims relating to a method for the productionthereof, as well as a packaging container produced from the packagingmaterial also account for these selective criteria.

According to the present invention, a barrier layer comprising a waterdispersible or soluble polymer, starch or starch derivate and amorphousSiO₂ will thus be optimised in terms of the quantity of SiO₂ in thelayer and also the particle size of the SiO₂ particles. It has alsoproved that the selected type of SiO₂ particles, as well as possibly theconfiguration of the SiO₂ particles may have an effect on the barrierproperties, there being indications that the configuration should bespherical or substantially spherical. However, it may not be ruled outthat other configurations may also give the effect according to thepresent invention. According to the present invention, it hassurprisingly proved that considerably better barrier properties inrespect of oxygen gas may be attained than those barrier propertieswhich could be expected on the basis of an accepted calculation modelfor the influence on filler agent in an oxygen gas barrier layer. It hasfurther surprisingly proved that the addition of SiO₂ particles in thebarrier layer gives a considerable increase in rigidity in the laminate.

Without locking the present invention to any given theory in respect ofincreased oxygen gas barrier, it is assumed that the colloidal particlesof SiO₂ function as a seedbed for the crystalline growth of the polymer,with improved crystallinity as a result and thereby improved oxygen gasbarrier effect, as well as improved resistance to liquids. However,theories are yet to be established concerning the reason for the optimumwhich has been found in certain quantities of SiO₂ and certain particlesizes—the results are truly surprising.

The barrier layer according to the present invention may be utilised forimproved barrier properties in packaging laminates of conventional type,with conventional surface weights or grammage of the barrier layerand/or may be utilised for retained barrier properties in a packaginglaminate of known type, with lower surface weights or grammage thanpreviously.

In addition to those advantages already mentioned, the present inventionentails that the improved liquid resistance and increased oxygen gasbarrier in the layer of polymer, starch or starch derivate and SiO₂ canbe attained without increased costs, since the silica is normally notmore expensive than the polymer, starch or starch derivate. Furthermore,the advantage will be afforded that the total solids of the dispersioncan be increased without a deterioration in viscosity (i.e. withoutviscosity increasing). This is an advantage since it implies less dryingenergy at the same time as good properties for application of the layerare maintained. At, for example, a 60% admixture of silica, the totalsolids may be increased from 10% to 18%, from 12% to 20.7% or from 15%to 24% with retained viscosity. In addition, the advantage will furtherbe attained that layers of aluminium foil or other gas barrier layersapart from that layer according to the present invention, may be avoidedin the packaging laminate.

DETAILED DESCRIPTION OF THE INVENTION

The barrier layer comprises more than 40 weight %, preferably more than45 weight %, even more preferably more than 50 weight % and mostpreferably more than 55 weight % but less than 80 weight %, preferablyless than 75 weight %, even more preferably less than 70 weight % andmost preferably less than 65 weight % of particles of amorphous,colloidal SiO₂, calculated on dry weight. In the examples, the selectiveeffect which is achieved in the preferred contents of SiO₂ is accountedfor.

The lower limit for the particle size of the SiO₂ particles isdetermined in practice by how small particles it is possible tomanufacture. Consequently, the particle size is at least 3 nm,preferably at least 4 nm and even more preferably at least 5 nm, eventhough even smaller particles could be utilised if they could bemanufactured. The upper limit is set by the fact that the particles mustbe able to be present in a stable colloidal sol. Consequently, theparticle size is at most 150 nm, preferably at most 100 nm and mostpreferably at most 70 nm.

It has further proved that also the type of SiO₂ particles is ofimportance for the effect according to the present invention. EkaChemicals within the Akzo Nobel group markets colloidal SiO₂ sols underthe trade mark Bindzil® as well as Nyacol®, of which at least a part isparticularly suitable for utilisation in connection with the presentinvention. These sols include SiO₂ particles in the above-disclosed sizerange in contents of 7-50 weight % and display viscosities of at most 50MPas, in most cases at most 20 MPas. The Bindzil type further displays aspecific area weight of between 80 and 500 m²/g.

According to one aspect of the present invention, said polymerdispersion or solution is based on a polymer which includes functionalhydroxyl groups or functional carboxyl groups.

According to another aspect of the present invention, the dispersible orsoluble polymer preferably consists of a polymer which per se displaysoxygen gas barrier properties.

According to still a further aspect of the present invention, thedispersible or soluble polymer, starch or starch derivate insteadconsists of a polymer, starch or starch derivate which per se does notdisplay any appreciable oxygen gas barrier property, the oxygen gasbarrier property being achieved by means of the admixture of SiO₂particles according to the present invention.

Most preferably, said polymer dispersion or solution is based on apolymer in the group essentially comprising ethylene acrylic acidcopolymers, ethylene methacrylic acid copolymers, ethyl vinyl acetatecopolymers, ethylene vinyl alcohol copolymers, modified ethylenecopolymers, polyvinyl alcohol, styrene copolymers and combinationsthereof. However, the present invention is not restricted to thesepolymers but other dispersible or soluble polymers are also conceivable,in addition to starch or starch derivate.

An additive, for example a dispersion-stabilising agent, may also beincluded in the gas barrier composition, preferably in a quantity whichdoes not exceed about 1 weight percent of the dry coating.

In the preferred case that the polymer consists of polyvinyl alcohol,this should display a degree of hydrolysis of at least 98%, and a mol.weight of between 16000 g/mol and 200000 g/mol.

According to yet a further aspect of this preferred embodiment of thepresent invention, the composition for the barrier layer, in addition topolyvinyl alcohol and particles of SiO₂, may also include ethyleneacrylic acid copolymer (EAA) and/or inorganic lamellar material, socalled nanoparticles. The EAA copolymer should preferably be included inthe barrier layer in the proportion of approx. 1-20 weight %, calculatedon the dry weight of the coating. A possibly utilised inorganic lamellarmaterial should display those features which are accounted for in WO00/01715. Also in cases of other polymers, starch or starch derivatesaccording to the foregoing, the inorganic lamellar material may beutilised correspondingly.

It has, however, also highly surprisingly proved that EAA as solepolymer can give an oxygen gas barrier effect together with the SiO₂particles according to the present invention, and this despite the factthat EAA does not display any appreciable oxygen gas barrier propertiesin itself.

The core layer in the packaging material preferably consists of paper orpaperboard, normally of a surface weight or grammage of approx. 100-500g/m², preferably approx. 200-300 g/m². However, it is also conceivablethat the core layer may consist of a polymer material, preferably with acorresponding surface weight or grammage.

The barrier layer is preferably applied as a liquid film of awater-based composition, comprising a dispersion or solution of polymer,starch or starch derivate, as well as particles of SiO₂.

The barrier layer is preferably laid direct on the core layer or on acarrier layer using a coating technology, in a surface weight of about 1to 10 g/m², more preferably about 1 to 8 g/m², most preferably about 1to 5 g/m², calculated on dry weight. If the applied layer is too thin,the gas barrier properties may by too poor and if it is to thick thereis a risk that the barrier layer will become rigid and that cracks willbe formed therein.

In that case when a carrier barrier is utilised for the formation of thebarrier layer according to the present invention, this may consist ofpaper or plastic or plastic coated paper. If paper is employed, it ispreferably thin. According to one alternative, the carrier layerpreferably consists of paper of a surface weight or grammage of approx.5-35 g/m², for example 7-25 g/m², more preferably approx. 10-20 g/m².

The carrier layer with the barrier layer and the core layer may beunited in different ways in accordance with that described in WO00/01715.

According to another embodiment of the present invention, the barrierlayer according to the present invention may be laminated to the corelayer by the intermediary of an interjacent polymer layer. Such aninterjacent layer, for example a polyethylene, may be applied on thecore layer in a first step, preferably by means of extrusion, whereafterthe gas barrier layer is applied on the interjacent layer in a secondstep.

According to still a further aspect of the present invention, anextremely good liquid resistance in the barrier layer will also beattained without heat treatment thereof, at least in cases of polyvinylalcohol as polymer, and a surprisingly good resistance to liquid isachieved after heat treatment. It is, therefore, to be preferred thatheat treatment be carried out on the barrier layer, once this has beenapplied on the core layer or on a carrier, and dried. The web surfacetemperature for the heat treatment (the curing) is preferably at least170° C. and even more preferably at least 200° C., in which event thetime elapsed should be as short as possible, typically of the order ofmagnitude of milliseconds, e.g. at most 100 ms and preferably at most 50ms.

Most preferably, the material comprising the polymer, the starch orstarch derivate and particles of SiO₂ is first dried at web surfacetemperatures of 80 to 160° C. (preferably 140-160° C.) in a first step,followed by curing at web surface temperatures of 170 to 230° C. in asecond step, which gives rise to an improved gas barrier at 80% RH.Possibly, the carrier material and the barrier material may be cooledbetween the two steps.

Preferably, the packaging laminate includes a polymer layer, preferablythermoplastic, e.g. polyethylene, laminated directly on the gas barrierlayer. Preferably, this plastic is LDPE. Other thermoplastics which maybe employed are other types of polyethylene (among others LLDPE, ULDPE,VLDPE, M-PE and HDPE), polypropylene and polyethylene terephthalate.

On the other side of the core layer, i.e. that side which is intended toconstitute the outside in the packaging container, there may be providedone or more other layers, including a layer for thermosealing, e.g. ofone of the previously mentioned thermoplastics.

According to still a further aspect of the present invention, apackaging container is also proposed which is produced by fold formationof a sheet or web of laminated packaging material according to thepresent invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will now be described in greater detailhereinbelow, with reference to one preferred embodiment and withreference to the accompanying Drawings. In the accompanying Drawings:

FIG. 1 schematically shows a cross section of a laminated packagingmaterial according to one preferred embodiment of the present invention;and

FIG. 2 schematically illustrates a method of producing the laminatedpackaging material according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

It should first be observed that the packaging material which is shownin FIG. 1 by no means limits the scope of the present invention, but ismerely intended to illustrate a conceivable, extremely simple,embodiment of the invention. Thus, the number of layers in the packaginglaminate may be varied, and also their composition may be varied freelyin accordance with the desired end product.

Referring to the Drawing, FIG. 1 schematically shows a cross section ofa laminate packaging material according to the present invention whichis generically designated 10. In the illustrated, simple, case, thelaminated packaging material comprises a core layer 11 of fibre materialor other suitable material, for example polymer material.

Examples of fibre material consist of paper or paperboard ofconventional quality for packaging laminates, while examples of suitablepolymer materials for the core layer 11 consist of polyolefin, e.g.polyethylene, polypropylene and copolymers, olefin monomers, polyester,polyamide etc. In the case where the core layer 11 consists of a polymermaterial, this material may display a homogeneous, solid structure ormay also consist of a foamed or expanded polymer. The polymer materialmay also consist of a filled polymer.

On both sides of the core layer 11, there are disposed outer,liquid-tight coating layers 12, 13 of plastic, which not necessarily butpreferably consist of extrudable thermoplastic, e.g. polyethylene, inaccordance with the foregoing. These layers also act as sealing layersfor thermosealing by means of conventional methods.

Between the core layer 11 and the one outer, liquid-tight coating layer12, there is provided a layer of a polymer, starch or starch derivate inaccordance with the foregoing, dispersible or soluble in water, in thispreferred case, polyvinyl alcohol (PVOH), which, according to theinvention, contains an optimated content of SiO₂ particles in accordancewith the foregoing.

The packaging laminate 10 illustrated in FIG. 1 may, according to thepresent invention, be produced in the manner which is schematicallyillustrated in FIG. 2.

A web 11 of paper, paperboard or polymer material is unrolled from amagazine reel 11′ and is led past an applicator 15, preferably a coater,which is disposed adjacent the web and by means of which a solution ordispersion of polyvinyl alcohol including SiO₂ is applied on the oneside of the web 11 in the form of a substantially continuous barrierlayer 14. It is generally known within the art that coating facilitatesthe formation of very thin layers in comparison with, for example,extrusion. By coating, well-formed layers which are as thin as 1 μm canbe realised, while layers thinner than about 5 μm cannot be realised byextrusion.

The web 11 is thereafter led further past a drying apparatus 16 whichacts on the coated side of the web 11, e.g. in the form of an infrareddryer or a hot air unit for driving off water and drying the appliedlayer 14.

Preferably, the dried web is thereafter heated up to at least 170° C. ina heat treatment unit 20 for curing the layer 14. The time for thecuring treatment may be extremely brief, corresponding to normallyemployed web speeds. The curing by heat treatment also results inconsiderably improved adhesion or bonding between the barrier layer 14and the core layer 11 or an interjacent layer.

The coated, dried and cured web 11 is finally led through a nip betweentwo rotating rollers 17, at the same time as thin plastic films 12 and13 are extruded on both sides of the web 11, with the aid of extruders18 and 19 for forming the finished packaging laminate 10 according tothe present invention.

From a sheet or a web-shaped packaging laminate 10 which, in a per seknown manner, has been provided with crease lines which facilitate foldforming, packages are formed in a per se known manner by rationalforming, filling and sealing technology (not shown). From, for example,a web of the packaging laminate 10, packaging containers may be producedin automatic packing and filling machines in such a manner that the webunwound from the magazine reel is reformed into a tube by the edges ofthe web being united in an overlap seal or joint, whereafter the thusformed tube is filled with the intended contents and divided intoindividual packaging containers by repeated transverse seals disposed inspaced apart relationship from one another and at right angles to thetube. Once the supplied contents have thus been enclosed in sealedsections of the tube, these sections are separated from the tube byincisions in the above mentioned transverse sealing zones. The severedtube sections are thereafter formed by folding along crease linesprovided in the packaging material to form packaging containers of thedesired configuration, e.g. parallelepipedic configuration.

EXAMPLE 1

The purpose of the initial experiment was to compare actual effect ofthe addition of colloidal SiO₂ on the oxygen gas barrier in a barrierlayer of PVOH in comparison with calculated effect in a filled polymer.The calculation model takes into account quantity and dimensions ofparticles (any whatever), in a filled polymer, and gives an estimationof expected oxygen gas permeability:P _(filled) =P _(polymer)(1+(length/2*height)*volume fraction)

This calculated oxygen gas permeability was thus compared with actualoxygen gas permeability in a barrier layer. For the barrier layer,polyvinyl alcohol was mixed with colloidal silica in the quantities 5,50, 60 and 80 weight %, which corresponds to volume fractions of 0.03,0.35, 0.45 and 0.7, respectively. The silica particles displayed aparticle size (spherical) of 40 nm, i.e. corresponding to 40 nm Lengthand 40 nm height in the calculation model. The polyvinyl alcoholdisplayed a degree of hydrolysis of 99% and a mol. weight of 90000g/mol. The mixture was coated on 36 μm OPET film to a 5 μm thick layer(dry calculated) and dried at 150° C., whereafter the dried coatinglayer was heat treated for 4 minutes at 200° C.

Table 1 presents a comparison between calculated and actual effect onoxygen gas permeability at 23° C. and 83% RH. As will be apparent, asurprisingly good result is obtained at the measurement points 50 and 60weight %, i.e. oxygen gas transmissions which are greatly less thanthose expected from the calculation model.

TABLE 1 Oxygen gas Calculated oxygen Observed oxygen transmission PVOHgas transmission gas transmission (cm³/m² * SiO₂ (cm³/m² * (cm³/m² * 24h, 1 atm.) weight % 24 h, 1 atm.) 24 h, 1 atm.) 7.0 5 7.0 7.1-7.2 7.0 506.0 2.5-3.0 7.0 60 5.8 1.2-2.0 7.0 80 5.2 76-80

EXAMPLE 2

In a series of experiments, a series of samples was prepared in which anaqueous solution of 10 weight percent PVOH was heated to 60° C. andmixed with an aqueous dispersion at room temperature of SiO₂ particlesof the type Bindzil® 40/170 from Eka Chemicals. The polyvinyl alcoholdisplayed a degree of hydrolysis of 99%, a viscosity of 15% at 20° C. in4% solution and a mol. weight of 90000 g/mol. The mixture was mixed for4 minutes at 10000 rpm. After the mixing, the mixture was allowed tostand to the following day. The thus obtained mixture was employed fordispersion coating for the formation of a 5 μm layer (dry calculated) ona 36 μm OPET film, the film being dried at 150° C. The samples werecured for 4 minutes at 200° C. Measured oxygen gas transmission fordifferent contents of SiO₂ (dry calculated) is presented in table 2. Theresults constitute a mean value of two experiments and show that, incontents of SiO₂ up to 40 weight %, the oxygen gas barrier propertieswere not improved, but on the contrary deteriorated. Between 50 and 70weight % occurs a surprising effect, the oxygen gas transmission fallingdrastically. Best results were obtained at about 60 weight % SiO₂. At 80weight %, no oxygen gas barrier effect was achieved at all.

The obtained oxygen gas transmission has been analysed at about 83% RHin the experiments, i.e. a relatively humid atmosphere. The good resultswhich occur despite this humid atmosphere show that the gas barrierlayer according to the present invention displays extremely goodresistance to liquid, simultaneously with good gas barrier properties,which possibly, but not indisputably, may depend upon a higher level ofcrystallinity in the polyvinyl alcohol.

TABLE 2 Oxygen gas transmission SiO₂ (%) (cm³/m² * 24 h, 1 atm.) 0 6.310 7.1 20 9.2 30 8.1 40 6.0 50 3.7 60 1.3 65 2.5 70 3.5

EXAMPLE 3

In an experiment series, a series of samples was prepared in the samemanner as in example 2. Measured oxygen gas transmission for differenttypes and contents of SiO₂ (dry calculated) is presented in table 3. Theresults constitute mean values of two experiments and substantiate theillustrated optimum at about 50-70 weight %. Also in the admixture ofnanoparticles of inorganic lamellar material, the desired effect isattained. At the same time, the result shows that it is not all types ofSiO₂ particles which give the desired effect. For example, Eka Np 090gives a poorer oxygen gas barrier compared with the reference, as doeslikewise Bindzil NH3 30/220. On the other hand, with Bindzil 50/80 theeffect according to the present invention is attained. (In thedesignation XX/YYY in the Bindzil products, XX constitutes the weight %SiO₂ in the silica sol which is mixed together with the polyvinylalcohol, while the designation YYY constitutes the specific area weightin m²/g SiO₂ particles.)

TABLE 3 Oxygen gas transmission, cm³/m²/24 h/5 μm SiO₂ P = 1 atm Non 6.7 5% Bindzil 40/170 7.3 50% Bindzil 40/170 2.8 60% Bindzil 40/170 1.3 70%Bindzil 40/170 3.5 80% Bindzil 40/170 No barrier 50% Bindzil 40/170 +1.9 10% nanoparticles 50% Eka Np 090 9.8 50% Bindzil 50/80 3.7 60%Bindzil NH3 30/220 11.0 65% Bindzil NH3 30/220 27.4 70% Bindzil NH330/220 31.2

EXAMPLE 4

Dispersions of ethylene acrylic acid copolymer (EAA) (Epotal 2343, BASF,Germany) and SiO₂ particles were mixed together. The resultingdispersions were applied on OPET film (Melinex 800, Du Pont, 36 μm) in aHirano lab coater (1 m/min) and dried at 150° C. The coating thicknesswas 5 μm dry. Table 4 shows the resulting oxygen gas barrier in thecoating (the barrier effect of the OPET film has been discounted in thecalculation). The result surprisingly shows that EAA, which has noappreciable oxygen gas barrier effect per se, achieves oxygen gasbarrier effect when mixed with SiO₂ particles according to the presentinvention.

TABLE 4 Oxygen gas Particles/ transmission, Polymer, cm³/m²/24 h/5 μmSample %/% % RH P = 1 atm Epotal  —/100 50 No barrier ReferenceBindzil/Epotal 40/60 50 419 (40/170) Bindzil/Epotal 50/50 50 648(40/170) Bindzil/Epotal 50/50 50 648 (30/220) Bindzil/Epotal 60/40 501332 (30/220)

EXAMPLE 5

Dispersions of PVOH and SiO₂ particles were mixed together. Theresulting dispersions were applied on paperboard and thereafter dried.Table 5 shows the resulting flexural rigidity in paperboard which hadbeen coated with these dispersions in a comparison with coating solelywith PVOH. The result shows a surprising increase in rigidity in themachine direction (MD) of the paperboard. In the cross direction (CD) noappreciably improved rigidity was noted however.

TABLE 5 Flexural Increase in Particles/ rigidity, flexural rigidity,Polymer, Coating, mN mN/g Sample %/% g/m² MD CD MD CD Paperboard — —333.5 145.9 — — Reference PVOH  —/100 3.4 337.4 157.2 1.1 3.3 ReferencePVOH/Bindzil 30/70 7.2 349.6 158.8 2.2 1.8 (40/170) PVOH/Bindzil 40/607.5 347.8 168.9 1.9 3.1 (40/170) PVOH/Bindzil 50/50 9.1 376.0 173.6 4.73.1 (40/170) PVOH/Bindzil 60/40 11.5 379.8 193.6 4.0 4.2 (40/170)PVOH/Bindzil 30/70 8.1 361.2 168.4 3.4 2.8 (30/220) PVOH/Bindzil 40/607.6 370.8 170.4 4.9 3.2 (30/220) PVOH/Bindzil 50/50 11.4 364.9 171.4 2.82.2 (30/220) PVOH/Bindzil 60/40 10.7 379.2 176.2 4.3 2.8 (30/220)

The present invention is not restricted to the embodiments described inthe foregoing, but may be varied without departing from the scope of theappended claims.

1. A laminated packaging material comprising a core layer and a barrierlayer formed from a liqueform composition comprising a dispersion or asolution of a polymer, starch or starch derivate, on one side of thecore layer, the barrier layer also including particles of amorphous SiO₂, wherein said particles of amorphous SiO₂ are present in colloidalparticle size in said barrier layer in a content above 40 weight % butbelow 80 weight %, wherein said particles of amorphous, colloidal SiO₂have a particle size of at least 3 nm and at most 150 nm, and whereinsaid particles of amorphous, colloidal SiO₂ have a specific area weightof 80-170 m²/g, wherein said dispersion or solution is formed from apolymer which comprises functional hydroxyl groups or functionalcarboxyl groups, wherein said core layer consists of a layer of paper orpaperboard, and wherein the laminate packaging material furthercomprises outer, liquid-tight coatings of polymer material.
 2. Thelaminated packaging material as claimed in claim 1, wherein saidparticles of amorphous, colloidal SiO₂ are present in said barrier layerin a content above 45 weight %, but below 75 weight %.
 3. The laminatedpackaging material as claimed in claim 2, wherein said particles ofamorphous, colloidal SiO₂ are present in said barrier layer in a contentabove 50 weight % and below 70 weight %.
 4. The laminated packagingmaterial as claimed in claim 3, wherein said particles of amorphous,colloidal SiO₂ are present in said barrier layer in a content above 55weight % and below 65 weight %.
 5. The laminated packaging material asclaimed in claim 1, wherein said particles of amorphous, colloidal SiO₂have a particle size of at least 4 nm and at most 100 nm.
 6. Thelaminated packaging material as claimed in claim 5, wherein saidparticles of amorphous, colloidal SiO₂ have a particle size of at least5 nm and at most 70 nm.
 7. The laminated packaging material as claimedin claim 1, wherein said dispersion or solution is based on a polymerselected from the group consisting of ethylene acrylic acid copolymers,ethylene methacrylic acid copolymers, ethylene vinyl acetate copolymers,ethylene vinyl alcohol copolymers, modified ethylene copolymers,polyvinyl alcohol, styrene copolymers, and combinations thereof.
 8. Thelaminated packaging material as claimed in claim 1, wherein said barrierlayer a surface weight, dry calculated, of about 1-10 g/m².
 9. Thelaminated packaging material as claimed in claim 6, wherein said barrierlayer has a surface weight, dry calculated, of about 1-8 g/m².
 10. Thelaminated packaging material as claimed in claim 9, wherein said barrierlayer has a surface weight, dry calculated, of about 1 -5 g/m².
 11. Thelaminated packaging material as claimed in claim 1, wherein the outer,liquid-tight coatings are of a thermoplastic polymer material.
 12. Thelaminated packaging material as claimed in claim 1, wherein said barrierlayer is in direct contact with said core layer and well integratedtherewith, throughout substantially all of their surfaces facing towardsone another.
 13. The laminated packaging material as claimed in claim 1,wherein said barrier layer is indirectly applied against said core layerand well integrated therewith, throughout substantially all of theirsurfaces facing towards one another, an interjacent layer of a polymermaterial being disposed between them.
 14. A packaging container suitablefor containing foods, wherein it is formed from a laminate packagingmaterial as claimed in claim
 1. 15. A method of producing a laminatedpackaging material comprising a core layer and a barrier layer formedfrom a liqueform composition comprising a dispersion or solution of apolymer, starch or starch derivate, on one side of the core layer, thebarrier layer also including particles of amorphous SiO₂ , the processcomprising applying a barrier layer of a liqueform compositioncomprising a dispersion or solution of a polymer, starch or starchderivate, including said particles of amorphous SiO₂which have colloidalparticle size, in a content of above 40 weight % but below 80 weight %dry calculated, on one side of the core layer, wherein said particles ofamorphous, colloidal SiO₂ have a particle size of at least 3 nm and atmost 150 nm, and wherein said particles of amorphous, colloidal SiO₂have a specific area weight of 80-170 m²/g, wherein said dispersion orsolution is formed from a polymer which comprises functional hydroxylgroups or functional carboxyl groups, wherein said core layer consistsof a layer of paper or paperboard, and wherein the laminate packagingmaterial further comprises outer, liquid-tight coatings of polymermaterial.
 16. The method as claimed in claim 15, wherein said barrierlayer includes said particles of amorphous, colloidal SiO₂ in a contentabove 45 weight % but below 75 weight %.
 17. The method as claimed inclaim 16, wherein said barrier layer includes said particles ofamorphous, colloidal SiO₂ in a content above 50 weight % and below 70weight %.
 18. The method as claimed in claim 17, wherein said barrierlayer includes said particles of amorphous, colloidal SiO₂ in a contentabove 55 weight %, and below 65 weight %.
 19. The method as claimed inclaim 15, wherein said particles of amorphous, colloidal SiO₂ arespherical or substantially spherical.
 20. The method as claimed in claim15, wherein said dispersion or solution is based on a polymer selectedfrom the group consisting of ethylene acrylic acid copolymers, ethylenemethacrylic acid copolymers, ethylene vinyl acetate copolymers, ethylenevinyl alcohol copolymers, modified ethylene copolymers, polyvinylalcohol, styrene copolymers and combinations thereof.
 21. The method asclaimed in claim 15, wherein said barrier layer is applied with asurface weight, dry calculated, of about 1-10 g/m².
 22. The method asclaimed in claim 21, wherein said barrier layer is applied with asurface weight, dry calculated, of about 1-8 g/m².
 23. The method asclaimed in claim 22, wherein said barrier layer is applied with asurface weight, dry calculated, of about 1-5 g/m².
 24. The method asclaimed in claim 15, wherein said barrier layer is applied in the formof a liquid film of a liquid barrier composition, by means of a coatingprocess.
 25. The method as claimed in claim 15, wherein said barrierlayer is applied in the form of a liquid film of a liquid barriercomposition, on at least one side of a carrier layer and is dried duringheating, whereafter the carrier layer with the applied, dried barrierlayer is combined and permanently united with one side of the corelayer.
 26. The method as claimed in claim 15, wherein said barrier layeris dried in a first step, whereafter said barrier layer is cured by heattreatment at a web surface temperature of at least 170° C.
 27. Themethod as claimed in claim 26, wherein said barrier layer is dried at aweb surface temperature of 80-160° C., in a first step, whereafter saidbarrier layer is cured by heat treatment at a web surface temperature ofat least 170° C.
 28. The method as claimed in claim 27, wherein saidbarrier layer is dried at a web surface temperature of 140-160° C., in afirst step, whereafter said barrier layer is cured by heat treatment ata web surface temperature of at least 200° C., but at most 230° C. 29.The method as claimed in claim 15, wherein the outer, liquid-tightcoatings are of a thermoplastic polymer material.
 30. The method asclaimed in claim 15, wherein said particles of amorphous, colloidal SiO₂have a particle size of at least 4 nm and at most 100 nm.
 31. The methodas claimed in claim 30, wherein said particles of amorphous, colloidalSiO₂ have a particle size of at least 5 nm, and at most 70 nm.